Under certain conditions, hydrogen can accumulate in the interior of battery-powered appliances. The hydrogen may be released from the battery, or may be created by electrolysis outside the battery. Mixing of this hydrogen with ambient oxygen can form an explosive gas, which could potentially be ignited by a spark from the motor or switch of the device.
This problem has been addressed in various ways. In appliances and devices that do not need to be water-tight, the housing of the device will often contain an opening through which gases can vent.
In the case of devices that are operated in wet environments, for example electric toothbrushes and battery powered razors, the opening may be covered by a microporous membrane. The membrane is permeable to hydrogen gas, but impermeable to water. While this approach is generally effective in venting hydrogen from the interior of the device, the use of a membrane tends to be expensive and to increase the complexity of the product assembly process.
Another approach involves reacting the hydrogen gas rather than venting it. In this case, a hydrogenation catalyst is provided within the device to cause the hydrogen gas to react with oxygen and form water, and a silica dessicant is provided to absorb the water. Water-tight cameras utilizing this approach are described in U.S. 2002/0045093.